Metaballs and particles
You don't need to parent the Particles to the Metaball.
You want the particles to become metaballs. you achieve this by changing the rendering object of the Particle system. In your screenshot the particles are set to "halo". Go to the Render-Section of your particle system and change that to "object" (yellow rectangle) and select your metaball. The particles themselves are now metaballs and can interact with each other.